v1.6.18 gives the following error in console:
Error while compiling: LightsOn.cs(2264,29): error CS0584: Internal compiler error: Object reference not set to an instance of an object

Do I have to redownload the install files or something instead of updating?

That error doesn't appear to be related to the plugin, but rather the compiler. You'd need to check your logs for the full error though.

Correct. Had to update outdated wget.exe in .bat file and problem solved.